Learn Italian: Il tavolo di legno è pesante.

In Italian, you generally don't use adjectives to describe what something is made of. Instead, you use the preposition di (of) followed by the material noun. So, di legno literally translates to "of wood."

Does the adjective pesante change if the noun is feminine?

No, it stays exactly the same! Adjectives that end in -e in the singular (like pesante) are used for both masculine and feminine nouns. They only change to an -i ending in the plural.

I've heard the word tavola before. Why does this sentence use tavolo?

Both words mean "table," but they are used differently. Il tavolo refers to the physical piece of furniture itself, which fits perfectly here since we are describing its material and weight. La tavola is mostly used when talking about a table that is set for a meal.

Why does è have an accent mark?

The accent mark is crucial because it changes the meaning of the word entirely. è (with the accent) is the verb meaning "is", while e (without the accent) means "and".